This is the tenth of ten (10) engagements recorded in the "CSA Siege of Washington" from March 30—April 20, 1863.  

"On Monday morning [April 20th], having fully concerted the operation with Colonel Jones and Colonel Jourdan, I directed these zealous and energetic officers to advance, maintaining a constant communication with each other until the long sand ridge should be fully explored. The troops of the two camps moved at the same time. The left wing extended to the Dover road and scoured to the right and left of the railroad through most difficult ground; the right advanced by the open country bordering the Dover road and dashed first into the Sandy Ridge region, when they were opposed by skirmishers.

"The noise of this conflict was the first communicaiton the left was able to obtain with the right, although nearly abreast with it. The enemy's pickets on the railroad retired along the track, firing, thus giving distant notice of our progress there. Arriving at the Biddle road, an avenue 1 mile long from the long sand ridge to the railroad, while the skirmish was going on, Colonel Jourdan moved rapidly to the right upon it, with a battalion, and in support. The affair concluded on the Dover road about a mile in advance of the avenue. At that place the Sandy Ridge declines into a swamp, and the last end of it was roughtly intrenched. The rapid movement and severe fire of the excellent skirmishers of the Fifty-eighth Pennsylvania and gallant charge of 17 cavalry of company H, Third New York Cavalry, under Sergeant Dow, leaping the intrenchments, drove the main body of the rebels into the swamp, and detained a commissioned officer and 27 enlisted men of the Forty-ninth North Carolina Regiment in our hands as prisoners.

"Our loss in this skirmish was 7 enlisted men of the Fifty-eighth Pensylvania Volunteers and 1 of Company H, Third Regiment New York Cavalry, wounded. Three horses of the same cavalry party were killed."

"Sir: I have to report to you that in the skirmish with the enemy April 20, 1 man was wounded and 3 horses killed and 1 revolver lost. Seventeen of my command were engaged, under the command of Sergt. Henry Dow. I was sick and could not take command.

"I am, respectfully yours,
"John M. Willson,
"Captain, Third New York Cavalry, Commanding Station."

"Sir: I have the honor to report that I advanced on the Dover road this morning according to arrangements. No enemy were found this side of Sandy Ridge, but at the junction, or just beyond the causeway running from the railroad, fire was opened on my skirmishers. I had three companies deployed, which drove the enemy gradually back, they making a stand at every strong position. Near the upper end of the ridge, where it is not more than 100 yards wide, they had a breastwork of logs and earth reaching across to the swamps on both flanks, which they endeavored to hold and defended with great resolution. Finding the front likely to cost me many men, I deployed two more companies on the right and left flanks, with directions to force their way through the swamps. Those swamps were barely passable by woodmen, but my men succeeded in advancing on the flank of the breastwork, when they raised a shout, at which the enemy abandoned it, and fled into the swamp to the rear of the ridge.

"I cannot speak too highly of the conduct of my officers and men, of their coolness and steadiness under fire, and of their perserverence in pushing the enemy. The enemy opposed to us were one company of Nethercutt's battalion and three compaines of the Forty-ninth North Carolina, Lieutenant-Colonel Flemming, and they number, one of the prisoners says, 225. We found one of the enemy dead on the field (whom we buried decently), 2 wounded and took 27 prisoners.

"Our loss is 8 wounded, one of whom belongs to Company H, Third New York Cavalry, which company behaved gallantly and lost 3 horses. The breastwork where the enemy made their final stand is at the upper end of the ridge, about 6 miles by the Dover road from Core Creek; beyond, that road runs principally through swamps to its junction with the railroad.

"Very respectfully, your obedient servant.

"J. Richter Jones,
"Colonel Fifty-eighth Regiment."

"Yesterday there was another skirmish on Sandy Ridge; three companies of the Forty-ninth and about 70 of [Maj. John H.] Nethercutt's men, [8th NC Battalion-Partisan Rangers]. The enemy was first driven back, but got a strong re-enforcement and in turn we had to retire. We had 1 killed, 6 wounded, and 12 or 14 missing. Three horses were killed by our men belonging to the [enemy's] field officers..."

Lt. Col. John A.Flemming — Commanding Officer,

49th NC Regiment Detachment:
Company A — Capt. George W. Lytle,
2nd Company B — "Cleveland Mountain Boys" — 1st Lt. Judson J. Magness,
Company C — Capt. Henry A. Chambers.

8th NC Battalion-Partisan Rangers Detachment:
Unidentified Company — Led by Unknown

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Brig. Gen. Henry Prince — Commanding Officer,
Chief of Staff — Maj. Charles FitzSimmons (3rd NY Cavalry),
Aide-de-Camp — Lt. Sherman Grieg (3rd NY Cavalry),

2nd Brigade, 5th Division — Col. James Jourdan,
158th NY Infantry Detachment:
5 Unidentified Companies — Led by Unknown,
132nd NY Infantry Detachment:
9 Unidentified Companies — Led by Unknown,
3rd MA Infantry Detachment:
9 Unidentified Companies — Led by Col. Silas P. Richmond,
8th MA Infantry Detachment:
4 Unidentified Companies — Led by Unknown,
Riggs' Battery Detachment of 4 Field Pieces - Led by Unknown,

58th PA Infantry — Col. John R. Jones,
8th MA Infantry Detachment:
1 Unidentified Battalion of the Remaining Companies — Led by Unknown.

3rd NY Cavalry Detachment:
Company H — Led by Sgt. Henry G. Dow

North Carolina Troops: 1861-1865, A Roster, Volume XII, P.9, PP.29-30, PP.45-46, PP.54-55.

Official Records of the Union and Confederate Armies, Series I, Volume XVIII, PP.225-226, PP.238-240, P.255.  

https://dmna.ny.gov/historic/reghist/civil/rosters/cavalry/3rdCavCW_Roster.pdf